1. Field of the Invention
The invention relates in general to electrical transformers, and more specifically to electrical power and distribution transformers used in the transmission and distribution of electrical energy.
2. Description of the Prior Art
Magnetic materials used in the magnetic cores of electrical power and distribution transformers have been improved greatly over the years, enabling the size and manufacturing costs of a transformer to be reduced. In general, the electrical steels used in transformers may be classified as: (1) hot rolled, non-grain oriented steels, such as AISI types M-14, M-15, M-17 and M-19; (2) cold rolled grain oriented silicon steels, such as AISI types M-4 through M-8 hereinafter referred to as regular B steels; and (3) high permeability grain oriented silicon steel, hereinafter referred to as high B steels, which are doped with various dopants to provide a B.sub.10 value in excess of 18.5 KG, compared with 17 to 17.5 KG for regular B steels.
The non-grain oriented steels of class (1) give a very poor performance when used in power and distribution transformers, and thus their usage is confined to small control and speciality transformers. The high B steels of class (3) above, cost more to produce and thus are more costly than regular B steels. While magnetic cores constructed of high B steels exhibit lower core losses than similar magnetic cores constructed of regular B materials, their higher initial cost generally more than offsets their advantages, and thus the regular B steels of class (2) above, are presently used for most of the power and distribution transformers manufactured at the present time.